The subject of the present invention is a catalytic process for the cleavage of liquid organic disiloxanes with chlorosilanes with the simultaneous production of organic chlorosilanes of the general formula R.sub.3 SiCl, and of organic siloxanes of the general formula R".sub.4-n Si(OSiR.sub.3).sub.n, wherein R represents identical or different alkyl or aryl moieties, and wherein R" represents H, alkyl moieties of 1 to 18 carbon atoms, or aryl moieties, both being able to be substituted by the group ##STR1## and represents the grouping ##STR2##
The previous work on this reaction principle has been described thus far by J. R. Elliot et al. in J. Amer. Chem. Soc. 74, 1853 sqq. (1952), M. G. Woronkov et al. in J. Obsh. Chim. 29 (1959), 1508-1514, and in Dokl. Akad. Nauk SSSR 227 (1976)(2), eng., 198-201, and in U.S. Pat. Nos. 3,065,252 (1962) and 3,101,361 (1963).
The average person skilled in the art learns from these works that both the few chlorosilanes tested and the siloxanes have quite different reactivities, but that generally the tendency is towards very slow reactions, and that the reaction as a rule remains incomplete, but at the same time not only momomeric but to some extent also polymeric siloxanes containing Si--Cl are formed. The yields of Si--Cl--free persilylated products obtained thus far are too low for economically profitable uses, although a whole series of such products are susceptible of significant applications. The problem therefore existed of finding for this process, which is known in itself, an embodiment making it possible to accelerate the reaction, block off possible secondary reactions, and increase the yields considerably.
A method has now been found for the cleavage of organodisiloxanes of the general formula (R.sub.3 Si).sub.2 O, in which R represents identical or different, saturated or unsaturated alkyl moieties of 1 to 18 carbon atoms, substituted if desired by ester, halogen or aryl moieties, or represents aryl moieties substituted if desired with chlorosilanes of the general formula EQU R'.sub.4-n SiCl.sub.n (n=2, 3 or 4)
wherein R' represents H and/or R, these moieties also being able to be substituted by the group ##STR3## (m=0 or 1 or 2), or it represents the moiety of the formula ##STR4## in which R has the same meaning as above and p can have a value of from 0 to 4, with the simultaneous production of organochlorosilanes of the general formula R.sub.3 SiCl and of organosiloxanes of the general formula R".sub.4-n Si(OSiR.sub.3).sub.n, in which R" is the same as R' and/or represents the grouping ##STR5## by performing the reaction in the presence of ferric chloride and catalytic amounts of hydrochloric acid.
This method offers a decided advance in regard to yield, product quality, and general usefulness, which was not to have been expected on the basis of the former state of knowledge.
The method of the invention is performed simply by mixing the siloxane component (R.sub.3 Si).sub.2 O with the chlorosilane component R'.sub.4-n SiCl.sub.n and the ferric chloride catalyst, and starting the reaction by feeding into it a catalytic amount (0.05 to 1% by weight) of gaseous hydrogen chloride, and controlling the reaction by stirring and temperature control, by cooling or heating if necessary, until the mixture has ceased to react. It can be advantageous from time to time to restore the catalytic level of the hydrogen chloride.
If desired, catalytic amounts of 0.02-0.5 weight-percent of phosphorus trichloride and about 0.05 to 1 weight-percent of hydrogen chloride are added to the mixture toward the end of the reaction. Conventional methods of distillation are used for the separation of the chlorosilane and, if desired, of the siloxanes.
The ferric chloride catalyst is used in substance or as a solution of 1 to 15% by weight of anhydrous iron(III) chloride, preferably in ketones. It is used in concentrations of between 0.01% and 10% of the amount of siloxane used.
The reaction temperature is not critical. It can be any temperature from ambient to the boiling temperature of the reaction system. A temperature range between 20.degree. and 55.degree. C. is preferred, and it is advantageous to keep the temperature below the boiling temperature of the reaction system so as to avoid hydrogen chloride losses.
Atmospheric pressure conditions are preferred. But it is possible to work in a pressure range between 1 and 10 Bar, too.
A reactor equipped for stirring and with heating and cooling systems is preferred as the apparatus for the practice of the method of the invention.
Disiloxanes are used as starting substances of the general formula (R.sub.3 Si).sub.2 O, especially hexamethyldisiloxane produced as waste in the synthesis of antibiotics; other examples are 1.2-divinyltetramethyldisiloxane, hexaethyldisiloxane, 1.2-di-3'-acetoxypropyltetramethyldisiloxane 1.2-dimethyltetraphenyldisiloxane, 1.2-di-tertiarybutyltetramethyldisiloxane, 1.2-bis-dodecyltetramethyldisiloxane and 1.2-di-2'-phenylethyltetramethyldisiloxane. It is a special advantage of the process of the invention that it can also operate with contaminated siloxanes such as, for example, siloxane containing solvents such as toluene or chloroform. Siloxanes containing amine are to be neutralized before use.
Chlorosilanes of many different kinds are used as starting substances of the general formula R'.sub.4-n SiCl.sub.n. Examples are: tetrachlorosilane, trichlorosilane, dichlorosilane, hexachlorodisiloxane, decachlorotetrasiloxane, methyltrichlorosilane, methylhydrogendichlorosilane, dimethyldichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, isobutyltrichlorosilane, octyltrichlorosilane, octadecyltrichlorosilane, vinyltrichlorosilane, vinylmethyldichlorosilane, 1.2-bis-trichlorosilylethane, 1.2-bis-trichlorosilylethylene, allyltrichlorosilane, propenyltrichlorosilane, chloromethylmethyldichlorosilane, 2-chloroethylmethyldichlorosilane, 3-chloropropyltrichlorosilane, 1-trichlorosilyl-1,3-butadiene, propinyltrichlorosilane, phenyltrichlorosilane, phenylmethyldichlorosilane, diphenyldichlorosilane, tolyltrichlorosilane, cyclohexadienyltrichlorosilane, bis-trichlorosilylbenzenes, bis-trichlorosilylcyclohexenes etc. Mixtures of these compounds can also be used.
The moiety R' can accordingly represent any like or unalike moieties from the group, hydrogen, alkyl, aryl or alkenyl, and they can be substituted, preferably terminally, by a halogen or an ##STR6## group. The moiety R' can also represent the grouping: ##STR7## wherein m can be equal to 0 to 3, and p equal to 0 to 4.
In the catalyst system, the use in accordance with the invention of catalytic amounts of hydrogen chloride together with ferric chloride (solid or dissolved), in the above-given concentrations, is effective in the scope of the method of the invention.
It has furthermore proven advantageous to use as the catalyst in accordance with the invention ferric chloride in the form of its addition complex compounds with compounds containing oxo groups, such as ketones, aldehydes or carboxylic acid chlorides, together with a catalytic amount of hydrogen chloride. Ketones are preferred. Oxo compounds--preferably ketones in accordance with the invention--form solvates with ferric chloride, an example being C.sub.6 H.sub.5 COCH.sub.3.FeCl.sub.3 from acetophenone (cf. Beilstein 7, IV 619), these solvates being always present in the solution of ferric chloride in the ketones, as can be proven by the infrared spectra; they are prepared in accordance with the invention by the simple dissolution of ferric chloride in the corresponding ketone, in the cold.
Ketones which are suitable for these catalytic purposes in accordance with the invention are, for example, acetone, 2-butanone, 4-methyl-2-pentanone, mesityl oxide, acetophenone, dibenzalacetone, benzophenone, and cyclohexanone. The special advantage of the use of such ketone solvates lies in the considerable acceleration of the reaction which is thereby achieved.
It is particularly in the case of reaction mixtures in which the speed of the reaction decreases with the progress of the reaction that the phosphorus trichloride co-catalyst, in the above-named concentrations, is used additionally, in combination with catalytic amounts of hydrogen chloride, and, in accordance with the invention, toward the end of the reaction. The phosphorus trichloride addition in accordance with the invention then brings about a more rapid completion of the remainder of the transformation reaction that is still to be expected. Surprisingly, this additional catalytic effect in accordance with the invention does not take place if the phosphorus trichloride is added to the reaction mixture at the outset, with or without the ferric chloride/hydrogen chloride/ketone catalyst of the invention.
Substances prepared by the method of the invention are, for example, the siloxane compounds of the general formula R".sub.4-n Si(OSiR.sub.3).sub.n, all obtainable from hexamethyldisiloxane, simultaneously with trimethylchlorosilane as a second product, which are listed herewith:
2.2.6.6-tetramethyl-4.4-bistrimethylsiloxy-2.4.6-trisila-3.5-dioxaheptane, PA0 2.2.6.6-tetramethyl-4-trimethylsiloxy-2,4,6-trisila-3.5-dioxaheptane, PA0 2.2.6.6-tetramethyl-2.4.6-trisila-3.5-dioxaheptane, PA0 2.2.8.8-tetramethyl-4.4.6.6-tetrakis-trimethylsiloxy-2.4.6.8-tetrasila-3.5. 7-trioxanonane, PA0 2.2.4.6.6-pentamethyl-4-trimethylsiloxy-2.4.6-trisilia-3.5-dioxaheptane, PA0 2.2.4.4.6.6-hexamethyl-2.4.6-trisila-3.5-dioxaheptane, PA0 2.2.6-trimethyl-4.4-bis-trimethylsiloxy-2.4-disila-3-oxaheptane, PA0 2.2-dimethyl-4.4-bis-trimethylsiloxy-2.4-disila-3-oxadocosane, PA0 2.2.6.6-tetramethyl-4-vinyl-4-trimethylsiloxy-2.4.6-trisila-3.5-dioxaheptan e, PA0 2.2.4.6.6-pentamethyl-4-vinyl-2.4.6-trisila-3.5-dioxaheptane, PA0 2.2.9.9-tetramethyl-4.4.7.7-tetrakis-trimethylsiloxy-2.4.7.9-tetrasila-3.8- dioxadecane, PA0 2.2.4.6.6-pentamethyl-4-chloromethyl-2.4.6-trisila-3.5-dioxaheptane, PA0 2.2-dimethyl-4.4-bis-trimethylsiloxy-2.4-disila-3-oxaheptane, PA0 2.2-dimethyl-4.4-bis-trimethylsiloxy-7-chloro-2.4-disilia-3-oxaheptane, PA0 2.2-dimethyl-4.4-bis-trimethylsiloxy-2.4-disila-3-oxaoctadiene-(5.7) PA0 2.2-dimethyl-4.4-bis-trimethylsiloxy-2.4-disila-3-oxaheptene-(6) PA0 2.2.6.6-tetramethyl-4-phenyl-4-trimethylsiloxy-2.4.6-trisila-3.5-dioxahepta ne, PA0 2.2.4.6.6-pentamethyl-4-phenyl-2.4.6-trisila-3.5-dioxaheptane, PA0 2.2.6.6-tetramethyl-4.4-diphenyl-2.4.6-trisila-3.5-dioxaheptane, PA0 2.2.4.6.6-pentamethyl-4-p-bromophenyl-2.4.6-trisila-3.5-dioxaheptane, PA0 2.2.6.6-tetramethyl-4-tolyl-4-trimethylsiloxy-2.4.6-trisila-3.5-dioxaheptan e, PA0 2.2.6.6-tetramethyl-4-cyclohexenyl-4-trimethylsiloxy-2.4.6-trisila-3.5-diox aheptane, PA0 2.2.6.6-tetramethyl-4-cyclohexadienyl-4-trimethylsiloxy-2.4.6-trisila-3.5-d ioxaheptane, PA0 Bis-(tris-trimethylsiloxy)silylbenzene isomers.
The following are additional examples of substances prepared by the method of the invention:
2.2.3.3.7.7.8.8-octamethyl-5-tert.butyldimethylsiloxy-3.5.7-trisila-4.6-dio xanonane and tert.butyldimethylchlorosilane from 1.2-ditert.butyltetramethyldisiloxane and trihlorosilane,
2.2.6.6-tetraphenyl-4.4-dimethyl-2.4.6-trisila-3.5-dioxaheptane and methyldiphenylchlorosilane from 1.2-dimethyltetraphenyldisiloxane and dimethyldichlorosilane,
1.5.5.9-tetraphenyl-3.3.7.7-tetramethyl-3.5.7-trisila-4.6-dioxanonane and dimethyl-2-phenylethylchlorosilane from 1.2-di-2-phenylethyltetramethyldisiloxane and diphenyldichlorosilane.
The chlorosilanes of the general formula R.sub.3 SiCl produced in the reaction of the invention are valuable intermediates and end products for which applications exist in protective-group chemistry. The organosiloxanes of the general formula R".sub.4-n Si(OSiR.sub.3).sub.n, some of them new, which can now be prpared in a simple and economical manner by the method of the invention, have a wide variety of valuable properties.
Organosiloxanes having a large proportion of branched, unsaturated and aromatic organosubstituents, which can be prepared by the method of the invention, are used to advantage as additives in heating and motor fuel oils, in concentrations between 0.05 and 0.8 weight-percent for keeping fuel gas and exhaust gas devices free of deposits caused by oil combustion, for making the combustion complete and thus increasing the energy yield, and for reducing the dangers of corrosion and atmospheric pollution involved in combustion processes.
Additional examples of applications are the use of such compounds, prepared by the method of the invention, as diffusion pump oils, such as for example the above-cited 2.2.6.6-tetraphenyl-4.4-dimethyl-2.4.6-trisila-3.5-dioxaheptane, as heat carrying liquids, and as conditioners for hydrophilic and hydrophobic phases.
The following examples will explain the invention, without, however, restricting it.